Dynamic characteristics of servo-controlled mobile robot using optimum pulse width modulation (PWM)

Abstract

A mobile robot is designed and fabricated using locally available hardware components. It is driven by two independently controlled rear wheels and one unpowered omni-directional wheel in the front. A PIC microcontroller based system is used to take control actions using the feed-back signals. The response of the robot to the control actions is monitored using PC interfaced data acquisition system. Experimentations provided temporal motion data from wheels of the robot, motor currents and battery voltages. Data thus obtained is analyzed to obtain the response of the system to the control actions. When the drive motors are identically powered, it is found that the robot's left wheel motor is slightly faster than the right wheel motor. Experiments are carried out to find optimum duty cycle for the left motor to provide similar characteristics of the right motor. The optimum duty cycle thus obtained is verified at different loading conditions. Effect of loading on motor currents and robot dynamics is also analyzed and the effect of dynamic braking is found satisfactory.